//============================================================================
//
//  This file is part of GPSTk, the GPS Toolkit.
//
//  The GPSTk is free software; you can redistribute it and/or modify
//  it under the terms of the GNU Lesser General Public License as published
//  by the Free Software Foundation; either version 3.0 of the License, or
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//
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//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public
//  License along with GPSTk; if not, write to the Free Software Foundation,
//  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110, USA
//
//  Copyright 2004, The University of Texas at Austin
//  Dagoberto Salazar - gAGE ( http://www.gage.es ). 2007, 2008, 2011
//
//============================================================================

//============================================================================
//
//This software developed by Applied Research Laboratories at the University of
//Texas at Austin, under contract to an agency or agencies within the U.S.
//Department of Defense. The U.S. Government retains all rights to use,
//duplicate, distribute, disclose, or release this software.
//
//Pursuant to DoD Directive 523024
//
// DISTRIBUTION STATEMENT A: This software has been approved for public
//                           release, distribution is unlimited.
//
//=============================================================================

/**
 * @file LICSDetector.hpp
 * This is a class to detect cycle slips using LI observables.
 */

#ifndef GPSTK_LICSDETECTOR_HPP
#define GPSTK_LICSDETECTOR_HPP

#include "ProcessingClass.hpp"



namespace gpstk
{

/** @addtogroup GPSsolutions */
//@{


/** This is a class to detect cycle slips using LI observables.
 *
 * This class is meant to be used with the GNSS data structures objects
 * found in "DataStructures" class.
 *
 * A typical way to use this class follows:
 *
 * @code
 *   RinexObsStream rin("ebre0300.02o");
 *
 *   gnssRinex gRin;
 *   ComputeLI getLI;
 *   LICSDetector markCSLI;
 *
 *   while(rin >> gRin)
 *   {
 *      gRin >> getLI >> markCSLI;
 *   }
 * @endcode
 *
 * The "LICSDetector" object will visit every satellite in the GNSS data
 * structure that is "gRin" and will decide if a cycle slip has happened
 * in the given observable.
 *
 * The algorithm will use LI observables, and the LLI1 and LLI2 indexes.
 * The result (a 1 if a cycle slip is found, 0 otherwise) will be stored
 * in the data structure both as the CSL1 and CSL2 indexes.
 *
 * This algorithm will use some values as maximum interval of time
 * between two successive epochs, minimum threshold to declare cycle
 * slip and LI combination limit drift.
 *
 * The default values are usually fine, but you may change them with the
 * appropriate methods. This is of special importance for the maximum
 * interval time, that should be adjusted for your sampling rate. It is
 * 61 seconds by default, which is appropriate for 30 seconds per sample
 * RINEX observation files.
 *
 * When used with the ">>" operator, this class returns the same incoming
 * data structure with the cycle slip indexes inserted along their
 * corresponding satellites. Be warned that if a given satellite does not
 * have the observations required, it will be summarily deleted from the
 * data structure.
 *
 * Be aware that some combinations of cycle slips in L1 and L2 may result
 * in a false negative when using a cycle slip detector based on LI.
 * Therefore, to be on the safe side you should complement this with
 * another kind of detector, such as one based on the Melbourne-Wubbena
 * combination.
 *
 * @sa MWCSDetector.hpp for more information.
 *
 * \warning Cycle slip detectors are objets that store their internal
 * state, so you MUST NOT use the SAME object to process DIFFERENT data
 * streams.
 *
 */
class LICSDetector : public ProcessingClass
{
public:

    /// Default constructor, setting default parameters.
    LICSDetector() : obsType(TypeID::LI), lliType1(TypeID::LLI1),
        lliType2(TypeID::LLI2), resultType1(TypeID::CSL1),
        resultType2(TypeID::CSL2), deltaTMax(61.0),
        minThreshold(0.04), LIDrift(0.002), useLLI(true)
    { };


    /** Common constructor
     *
     * @param mThr    Minimum threshold to declare cycle slip, in meters.
     * @param drift   LI combination limit drift, in meters/second.
     * @param dtMax   Maximum interval of time allowed between two
     *                successive epochs, in seconds.
     */
    LICSDetector( const double& mThr,
                  const double& drift,
                  const double& dtMax = 61.0,
                  const bool& use = true);


    /** Returns a satTypeValueMap object, adding the new data generated
     *  when calling this object.
     *
     * @param epoch     Time of observations.
     * @param gData     Data object holding the data.
     * @param epochflag Epoch flag.
     */
    virtual satTypeValueMap& Process( const CommonTime& epoch,
                                      satTypeValueMap& gData,
                                      const short& epochflag = 0 )
    throw(ProcessingException);



    /** Method to get the maximum interval of time allowed between two
     *  successive epochs, in seconds.
     */
    virtual double getDeltaTMax() const
    {
        return deltaTMax;
    };


    /** Method to set the maximum interval of time allowed between two
     *  successive epochs.
     *
     * @param maxDelta      Maximum interval of time, in seconds
     */
    virtual LICSDetector& setDeltaTMax(const double& maxDelta);


    /** Method to get the minimum threshold for cycle slip detection, in
     *  meters.
     */
    virtual double getMinThreshold() const
    {
        return minThreshold;
    };


    /** Method to set the minimum threshold for cycle slip detection, in
     *  meters.
     *
     * @param mThr    Minimum threshold for cycle slip detection, in
     *                meters.
     */
    virtual LICSDetector& setMinThreshold(const double& mThr);


    /// Method to get the LI combination limit drift, in meters/second
    virtual double getLIDrift() const
    {
        return LIDrift;
    };


    /** Method to set the LI combination limit drift, in meters/second
     *
     * @param drift     LI combination limit drift, in meters/second.
     */
    virtual LICSDetector& setLIDrift(const double& drift);


    /// Method to know if the LLI check is enabled or disabled.
    virtual bool getUseLLI() const
    {
        return useLLI;
    };


    /** Method to set whether the LLI indexes will be used as an aid
     *  or not.
     *
     * @param use   Boolean value enabling/disabling LLI check
     */
    virtual LICSDetector& setUseLLI(const bool& use)
    {
        useLLI = use;
        return (*this);
    };


    /** Returns a gnnsSatTypeValue object, adding the new data generated
     *  when calling this object.
     *
     * @param gData    Data object holding the data.
     */
    virtual gnssSatTypeValue& Process(gnssSatTypeValue& gData)
    throw(ProcessingException)
    {
        Process(gData.header.epoch, gData.body);
        return gData;
    };


    /** Returns a gnnsRinex object, adding the new data generated when
     *  calling this object.
     *
     * @param gData    Data object holding the data.
     */
    virtual gnssRinex& Process(gnssRinex& gData)
    throw(ProcessingException);


    /// Returns a string identifying this object.
    virtual std::string getClassName(void) const;


    /// Destructor
    virtual ~LICSDetector() {};


private:


    /// Type of observable.
    TypeID obsType;


    /// Type of LLI1 record.
    TypeID lliType1;


    /// Type of LLI2 record.
    TypeID lliType2;


    /// Type of result #1.
    TypeID resultType1;


    /// Type of result #2.
    TypeID resultType2;


    /// Maximum interval of time allowed between two successive epochs,
    /// in seconds.
    double deltaTMax;


    /// Minimum threshold to declare cycle slip, in meters.
    double minThreshold;


    /// LI combination limit drift, in meters/second.
    double LIDrift;


    /// This field tells whether to use or ignore the LLI indexes as
    /// an aid.
    bool useLLI;


    /// A structure used to store filter data for a SV.
    struct filterData
    {
        // Default constructor initializing the data in the structure
        filterData() : formerEpoch(CommonTime::BEGINNING_OF_TIME),
            windowSize(0), formerLI(0.0), formerBias(0.0),
            formerDeltaT(1.0)
        {};

        CommonTime formerEpoch;    ///< The previous epoch time stamp.
        int windowSize;         ///< Size of current window, in samples.
        double formerLI;        ///< Value of the previous LI observable.
        double formerBias;      ///< Previous bias (LI_1 - LI_0).
        double formerDeltaT;    ///< Previous time difference, in seconds.
    };


    /// Map holding the information regarding every satellite
    std::map<SatID, filterData> LIData;


    /** Method that implements the LI cycle slip detection algorithm
     *
     * @param epoch     Time of observations.
     * @param sat       SatID.
     * @param tvMap     Data structure of TypeID and values.
     * @param epochflag Epoch flag.
     * @param li        Current LI observation value.
     * @param lli1      LLI1 index.
     * @param lli2      LLI2 index.
     */
    virtual double getDetection( const CommonTime& epoch,
                                 const SatID& sat,
                                 typeValueMap& tvMap,
                                 const short& epochflag,
                                 const double& li,
                                 const double& lli1,
                                 const double& lli2 );


}; // End of class 'LICSDetector'

//@}

}  // End of namespace gpstk

#endif   // GPSTK_LICSDETECTOR_HPP
